The latest in a 147-year-long history of causeways connecting Galveston Island to the mainland is beautifully taking shape. Traylor Bros. Construction began work on the newest causeway October 13, 2003. When completed in mid-2008, a pair of 8,592-foot-long bridges separated by a scant 1 inch will create the appearance of a single bridge structure. Each 72-foot-wide deck will allow four lanes of traffic with 12-foot-wide shoulders inside and outside.
During construction of the first new bridge, traffic continued as normal on the existing causeway. Now completed, the new northbound bridge has been placed into service for both directions of traffic for the duration of construction.
Because the new southbound bridge will occupy the footprint of the bridges built in 1960 and 1979, demolition was a prerequisite to construction of the southbound bridge. Demolition began in the center of the bridges in March 2006 and worked toward the shore so that new construction could begin before demolition was complete. Staying ahead of new construction, demolition is expected to be completed in March 2007.
Traylor Bros. kept the majority of the demolition in-house, their crews utilizing pneumatic hammers mounted on excavators to break most of the concrete. Aggregate Technologies of Houston was subcontracted to cut the concrete deck into sections for easier removal. Traylor's large new Allied G130 pneumatic hammer then attacked the remainder of the structure down to water level.
Traylor Bros. tested several demonstration models of hydraulic hammers and chose the Allied brand — four of them. According to Dave Geddy, project superintendent, "Allied proved to be extremely reliable and was compact."
The largest model on the job, an Allied Construction Products, LLC G130 with 16,000 foot-pounds of impact, is mounted on a John Deere 550 excavator. Operating from a barge, the unit breaks columns loose from their footings, allowing one of the 275-ton cranes on the job to place the cap and columns onto another barge used to transport the large pieces to their shore yard. There, three smaller Allied hammers (a G110, a G90, and a S27) break the larger pieces so they can be hauled to the Southern Crushed Concrete facility on Galveston Island. Because the recycled concrete is from a TxDOT project, it will be used as base material on other state projects. The steel is transported to Holmes Road Recycling in Houston.
Traylor Bros. recently purchased a second Allied G130 hammer as a backup. "We run it during scheduled maintenance," said Darren Lueking. "Our technicians perform some of the preventive maintenance, but we take it to Waukesha-Pearce (WPI) here in Houston for tune-ups."
Four blasting events were subcontracted to Allen Thompson and Engineered Explosive Services of Helotes, Texas, to break up the foundations and abandoned basket pits below water level down to 2 feet below the mud line, Lueking explained. The concrete and steel debris were then grappled out of the water and hauled to the shore yard.
As of mid-January, demolition of the two older bridges was about 65-percent complete, according to Lueking. About 45,000 cubic yards of the estimated total 65,000 cubic yards of concrete have been removed.
As the center portion of the bridge was cleared by the demolition crew, the construction crew was able to begin working on pier tables and pier shafts for the main spans over the Intracoastal Channel. Pipe piles driven almost 100 feet into the bay bottom will form the support system for the center spans that rise to 73 feet above mean high water directly over the Intracoastal Waterway Channel.
Both bridges will be constructed of precast concrete beams placed atop 62 cast-in-place concrete bents with an approximate span length of 135 feet, except for the three cast-in-place segmented spans over the Intracoastal Channel. The two main piers on either side of the Intercoastal Channel will serve as the supports for the cast-in-place segmental spans over the channel. They are clipped rectangles in shape, designed as hollow split-columns to resist the out-of-balance loads during the cantilever construction of the span segments. At the base, the walls of the columns are about 5 feet thick, and 18 inches thick at the top.
On the south end approach, 2,500 precast concrete piles have been driven into the sand to stabilize the huge embankment that will join the bridge to land. Hubco Construction of Houston has been subcontracted to perform the dirt work and asphalt paving for the roadway approaches.
The contractor completed the first phase, the future northbound bridge, 97 days ahead of schedule, qualifying them to receive a performance bonus from TxDOT. Under the project management of Scott Turnpaugh, Traylor Bros. is currently about 100 days ahead of schedule on construction of the southbound bridge.